DH and I always went together. Brought along a notebook with a list of questions, as well as to write down information regarding treatments, weight, height, medications. Also loaded down the diaper bag with extra diapers, blanket, toys, formula & bottled water to mix with because we pretty much 4-6 hours in the exam room while doctors, respiratory therapist, dietician, etc. came in and out.
We also brought along magazines and some snacks, coffee/water for ourselves to keep us occupied while waiting. Hand sanitizer/wipes are a good idea, too. Since it's cold and flu season after you touch elevator buttons, pens, doorknobs, you'll want to clean off your hands before touching baby.
So sorry about the diagnosis. Just take it one step at a time.